The invention relates to a motor-compressor comprising a vibration motor having a rotationally vibrating drive shaft and a compressor having at least one piston which is linearly reciprocated by the motor shaft, which motor-compressor is accomodated in a housing.
Such a motor-compressor is known from EP-A-O, No. 155,057. In the motor-compressor described therein the rotationaly vibrating motion of the rotor is converted into a linearly reciprocating motion of the pistons by means of a transmission. The moving parts in conjunction with the forces exerted by the electric motor and the gas forces constitute a mass-spring system. The motor is powered with a frequency equal to the natural frequency of the mass-spring system. When rigidly suspended this motor-compressor exhibits a substantial imbalance caused by the mass inertia of the moving parts and by the non-centric arrangement of the cylinder relative to the rotor bearing. The nature of the imbalance is such that the use of eccentric weights to compensate does not provide a satisfactory solution.